SYNTHESIS AND BIODISTRIBUTION STUDY OF A CHLOROTOXIN DERIVATIVE PEPTIDE LABELED WITH IODINE-131 FOR TUMOR THERAPY

Introduction: Chlorotoxin is a 36-amino acid peptide found in the venom of the Leiurus quinquestriatus which blocks small-conductance chloride channels. Chlorotoxin binds preferentially to glioma cells that allow development of new methods for the treatment and diagnosis of several types of cancer. Due to this a chlorotoxin derivative was labeled with 131I and investigated further.
Methods: A chlorotoxin derivative was synthesized on a solid phase using a standard Fmoc strategy. Labeling with iodine-131 was performed through chloramine-T method and radiochemical analysis involved sephadex G-25 and HPLC methods. The stability of radiopeptide was checked in the presence of PBS and human serum at 37^oC up to 24 h. The biodistribution was studied in mice.
Results: The chemical purity of synthesized peptide as assessed by analytical RP-HPLC was 95%. Labeling of peptide resulted in a radiochemical yield of 80% with radiochemical purity of >95% with specific activity of 0.740 GBq/mmol. Results of In vitro studies demonstrated acceptable stability of compound in human serum and PBS solution.
Conclusion: Biodistribution data showed moderate blood clearance, with concentration of radioactivity in the kidneys, liver, intestine and stomach.